Alteration of distal tarsal subchondral bone thickness pattern in horses with tarsal pain.
Authors: Branch M V, Murray R C, Dyson S J, Goodship A E
Journal: Equine veterinary journal
Summary
# Editorial Summary: Distal Tarsal Subchondral Bone Changes in Equine Tarsal Pain Distal tarsal osteoarthritis remains poorly understood in terms of its underlying pathological development and the precise mechanisms generating pain, yet high-resolution magnetic resonance imaging (MRI) offers sensitivity to detect early structural changes that radiography may miss. Branch and colleagues used sagittal 3D T1-weighted MRI to map subchondral bone (SCB) thickness patterns across the central tarsal, third tarsal, and third metatarsal bones in 16 tarsal joints from horses with radiographically-evident tarsal osteoarthritis and three joints from horses with tarsal pain but normal radiographs, comparing these against known normal patterns. The critical finding was a fundamental reversal of the normal SCB thickness distribution: whereas sound horses typically display greater lateral SCB thickness at most sites, painful tarsi showed significantly greater medial SCB thickness throughout, alongside overall SCB thickening at the majority of measurement points. These altered loading patterns—evidenced by abnormal bone remodelling—suggest that different pathological processes may drive distal tarsal disease progression, making individual assessment of thickness distribution potentially valuable for understanding which joints are experiencing abnormal biomechanics. For practitioners, this work underscores the diagnostic value of MRI over radiography for early detection of tarsal pathology and hints that the location and pattern of bone changes might eventually help identify the functional or structural drivers of pain in individual cases, informing more targeted therapeutic approaches.
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Practical Takeaways
- •MRI can identify subchondral bone changes in painful tarsi before radiographic changes appear, potentially allowing earlier intervention in distal tarsal OA
- •The shift from lateral to medial subchondral bone thickening in painful joints may serve as an imaging indicator to distinguish pathological from normal tarsal adaptation
- •Different SCB thickness patterns suggest varying underlying pathological mechanisms in distal tarsal OA, which may eventually guide targeted treatment approaches
Key Findings
- •Horses with radiographic OA showed increased subchondral bone thickness medially and laterally compared to normal, with greater thickness at medial and lateral sites than midline on proximal and distal CT and T3
- •Painful tarsi demonstrated medial SCB thickness greater than lateral at all measured sites, opposite to the pattern in pain-free horses where lateral sites predominated
- •MRI-detected alteration of subchondral bone thickness patterns in painful tarsi suggests different pathological processes may underlie distal tarsal osteoarthritis development
- •Three horses with tarsal pain but no radiographic abnormalities were identified, indicating MRI may detect pathology before conventional radiography